Last frontiers are hard to find these days, but Paul Martin thinks he's found one: the pleasant land of counterpane, that which "knots up the ravelled sleave of care", kip: the one third of all human experience that has not been turned into lifestyle. Sleep is not just not lifestyle, it is becoming a shrinking, disregarded nuisance, a stumbling block on the road to the 24/7 society.

It is something of an embarrassment that in the time of the human genome we still don't really know what sleep is for. Of course it is restorative, but of what? Muscles merely need rest; the heart - the most active muscle of all - never stops. But the brain can't do with rest alone: the outside world has to be switched off, and creatures that are prevented from doing it altogether die.

Sleep and books about sleep are always with us. There was a surge of interest in the early 1980s, with Francis Crick, of DNA fame, together with Graeme Mitchison, proposing a new theory of dreams: to whit, that dreams are the brain's way of getting rid of the day's mental garbage. And lucid dreaming became briefly, pace my introduction, a lifestyle fad. Not a great deal has happened since then: Paul Martin's novelty is his polemical verve rather than any dramatic new theory.

Martin believes that most of us are sleeping less (1 hours a night on average) and that we won't get away with it: chronic lack of sleep increases the risk of heart attacks and strokes, reduces libido and all other prized functions, and is the main cause of road accidents (you can spot sleeper accidents by the lack of skid marks).

The purpose of sleep over mere rest seems to be the consolidation of memory and learning. Our memory does not work like a computer's, in which every piece of data simply has a unique location, like a pallet in the Ikea warehouse - B16, and so on. Far too much happens to us for that to be possible (and it would be robotic if it were). Instead, patterns of brain traces overlap; some are strongly etched, others weak. What happens in deep sleep is that the brain is very active, with the external senses switched off (but the eyes twitching), running over the day's traces. What we decided was important and made a great effort to learn, such as a new piece of music, is replayed quite a lot, while stray things that impinged on our consciousness only faintly are not played much and get drowned out by the stronger traces. We then wake up with some of yesterday's learning consolidated. Experiments in animals have shown identical brain traces during the learning experience and during REM sleep.

As with the Big Bang and the origin of the universe, there is a standard model of sleep and dreaming that has needed little correction since the 1960s. It all began in 1953 - the year of DNA - with the discovery by Eugene Aserinsky of REM sleep. REM stands for rapid eye movement: this is a paradoxical phase of sleep in which the brain becomes extremely active, although the senses are still shut down. This is the time of the most vivid and surreal dreams. There are five phases of sleep, REM being the last; the first four are known imaginatively as NREM (non-REM) sleep. Dreaming also occurs in NREM sleep but it tends to be prosaic. The cycle from falling asleep to completing REM sleep takes 90-100 minutes and in an average night we go through five such cycles.

It is because the sleep cycles are relatively inflexible that their disruption plays such havoc. The starkest example of this is the mayhem caused on the roads by drivers falling asleep. Everyone imagines that they can fight sleep off but this is an illusion. Post-Selby, drivers and the authorities are being forced to take this more seriously, but still British motorways lack the rest areas you find on the Continent.

Martin makes a powerful case for the need to take sleep seriously. There's no point working hard during the day to learn something only to skimp on sleep. Swotting up to the wire for an exam and not sleeping is a dumb idea. For Martin, sleep has become "the cultural equivalent of a 1950s British canteen meal: an inadequate and faintly unhealthy affair, indifferently concocted and consumed with more haste than enjoyment". His answer is that we should make a meal of it and become gourmet sleepers. He's also a great advocate of afternoon napping. A 20-minute nap in the middle of the day can work wonders for your efficiency afterwards. Northern Europe has always despised the siesta, but perhaps it is time to reconsider?

Paul Martin was a research biologist at Cambridge and Stanford before quitting to become a science writer. He writes what I still rejoice in calling natural history. He knows the research and quotes widely and appropriately from literature. You could see Counting Sheep as an antidote to the symptoms of the frenetic society delineated by James Gleick in Faster. I hope it does as well, either as an instant hit or as a sleeper.

· Peter Forbes is the translator of Primo Levi's The Search for Roots: A Personal Anthology

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